1. Field of the Invention
The present invention relates generally to the field of cancer biology. More particularly, it concerns the enumeration and isolation of circulating tumor cells to aid in early detection of tumors, metastases, and relapse.
2. Description of Related Art
Metastasis is the major cause for cancer-related deaths. Circulating tumor cells (CTC) are considered to be the seeds of metastasis and are defined as rare cells that detach themselves from the primary tumor into the blood stream and travel toward distant organs to colonize into metastases (Pantel and Brakenhoff, 2004). Although recent advances in the field of cancer therapy are able to contain the primary cancer from spreading, there is a need for a dependable biomarker for the early detection, diagnosis, and therapeutic monitoring of metastatic cancers. CTCs present in the peripheral blood of cancer patients are emerging as promising targets for early detection and monitoring therapeutic efficacy of anti-cancer drugs (Parkinson et al., 2012). At present, acceptable markers for detection of CTC include EpCAM and cytokeratins (Parkinson et al., 2012). However, these markers can detect only epithelial CTC, thereby excluding the epithelial-mesenchymal transformed (EMT) CTC that have lost expression of EpCAM (Sieuwerts et al., 2009) and any other non-epithelial CTC that originate from mesenchymal tumors, which constitute about 10% of adult and about 20% of pediatric cancer types (Mackall et al., 2002). This limitation of the current detection tools suggests a desperate need for novel tools that can fulfill these requirements.